Phosphorylation of SPOROCYTELESS/NOZZLE by the MPK3/6 Kinase Is Required for Anther Development

Abstract

Germ cells are indispensable carriers of genetic information from one generation to the next. In contrast to the well-understood process in animals, information on the mechanism of germ cell initiation in plants is very limited. / was previously identified as an essential regulator of diploid germ cell (archesporial cell) differentiation in the stamens and ovules of Arabidopsis (). Although () transcription is activated by the floral organ identity regulator AGAMOUS and epigenetically regulated by SET DOMAIN GROUP2, little is known about the regulation of the SPL protein. Here, we report that the protein kinases MPK3 and MPK6 can both interact with SPL in vitro and in vivo and can phosphorylate the SPL protein in vitro. In addition, phosphorylation of the SPL protein by MPK3/6 is required for SPL function in the Arabidopsis anther, as measured by its effect on archesporial cell differentiation. We further demonstrate that phosphorylation enhances SPL protein stability. This work not only uncovers the importance of SPL phosphorylation for its regulatory role in Arabidopsis anther development, but also supports the hypothesis that the regulation of precise spatiotemporal patterning of germ cell initiation and that differentiation is achieved progressively through multiple levels of regulation, including transcriptional and posttranslational modification.

Two young genes reshape a novel interaction network in Brassica napus

“…Bait and prey proteins were mixed at 4°C for 6 h and then purified using glutathione conjugated agarose beads (17-5132-01; GE Healthcare, San Ramon, CA, USA). In vitro binding was detected with western blot (Chou et al, 2006;Einarson et al, 2007;Zhao et al, 2017).…”

Diurnal changes in concerted plant protein phosphorylation and acetylation in Arabidopsis organs and seedlings

“…Similar to kinases and phosphatases involved in protein phosphorylation, protein acetylation is catalyzed by two families: the lysine acetyltransferases (KATs) and the lysine deacetylases (KDACs), which catalyze the addition and removal of acetyl groups from target proteins, respectively (Pandey et al ., ; Tran et al ., ; Uhrig et al ., ). Both protein phosphorylation and acetylation have been shown to regulate key cellular processes, such as glycolysis, nitrogen metabolism, photosynthesis (Finkemeier et al ., ; Engelsberger and Schulze, ; Menz et al ., ) and development (Han et al ., ; Zhao et al ., ). To date, protein phosphorylation and acetylation have each been characterized separately in plants, even though they may work synergistically or antagonistically to impact function when occuring on the same protein (Soufi et al ., ; Tran et al ., ; Mertins et al ., ; Rao et al ., ; Sharma et al ., ).…”

Proteomes and Phosphoproteomes of Anther and Pollen: Availability and Progress

“…Given the revealed extensive protein kinases during anther development, protein phosphorylation should play important roles in anther development. Recently, SPL was reported to be phosphorylated by MPK3/6 during anther development, demonstrating that protein phosphorylation is an important post‐translational modification regulating anther development. Therefore, systematical and comprehensive identification of phosphoproteins in anthers should be very useful for exploring the signaling pathways that mediate anther development and give insight into pathways and protein interaction networks underlying anther development.…”